获取img图片原始宽高

imgWH.src = 'http://asdfasdfadf.png';
imgWH.style.display = 'none';
// 图片加载完毕后执行
let w, h;
imgWH.onload = function () {
      if (imgWH.naturalWidth) {
              // HTML5 browsers
              w = imgWH.naturalWidth;
              h = imgWH.naturalHeight;
       } else {
               // 兼容IE6/7/8
               w = imgWH.width;
               h = imgWH.height;
        }
        console.log(w, h);
  };